Journal of Cluster Science ( IF 2.7 ) Pub Date : 2021-08-26 , DOI: 10.1007/s10876-021-02163-9 Ting-Chun Zhu 1 , Xiao-Hui Sun 1 , Juan Bai 2 , Yu-Feng Wang 2 , Hua-Hong Zou 2
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Abstract
Schiff base ligands with multiple chelating coordination sites are usually able to quickly capture lanthanide metal ions to form complexes, and it is difficult to twist and construct helical chains. In this work, we used 2-hydroxy-1-naphthaldehyde, propylenediamine, and Ln(NO3)3·6H2O to react at 80 °C in solvothermal to obtain chains [Ln = Dy (1); Ln = Gd (2)] with a helical structure. It is worth noting that 2-hydroxy-1-naphthaldehyde and propylenediamine undergo an in situ reaction under one-pot conditions to form ligand 1,1′-((1E,1′E)-(propane-1,3-diylbis(azaneylylidene))bis(methaneylylidene))bis(naphthalen-2-ol) (H2L). The ligand (L)2− bridges the two metal center Ln(III) ions with a monodentate, causing it to twist into an “S” shape and further form a helical chain. In addition, the independent unit of the helical chain is a single core, and its metal center is in the O9 coordination environment provided by the ligand and the end group coordination NO3− ions. What’s more noteworthy is that chain 1 exhibits single-molecule magnet (SMM) behavior, and its SMM performance is significantly improved under the DC field induction condition of 600 Oe. By Debye model fitting, the effective energy barrier of 1 is 17.8 K, and the relaxation time is 2.4 × 10–6 s. The magnetocaloric effect test of chain 2 is further carried out. When ΔH = 7 T and T = 2 K, its − ΔSm reaches the maximum value of 16.19 J K−1 kg−1.
Graphic Abstract
中文翻译：
由原位席夫碱反应构建的镧系基螺旋链：结构和磁性
摘要
具有多个螯合配位点的席夫碱配体通常能够快速捕获镧系金属离子形成配合物，并且难以扭曲和构建螺旋链。在这项工作中，我们使用 2-羟基-1-萘醛、丙二胺和 Ln(NO 3 ) 3 ·6H 2 O 在 80 °C 下溶剂热反应得到链 [Ln = Dy ( 1 ); Ln = Gd ( 2 )] 具有螺旋结构。值得注意的是，2-羟基-1-萘醛和丙二胺在一锅条件下进行原位反应，形成配体1,1'-((1 E ,1' E )-(propane-1,3-diylbis (azaneylylidene))bis(methaneyllidene))bis(naphthalen-2-ol) (H 2L)。配体 (L) 2-将两个金属中心 Ln(III) 离子与单齿连接起来，使其扭曲成“S”形并进一步形成螺旋链。此外，螺旋链的独立单元为单核，其金属中心处于配体和端基配位NO 3 -离子提供的O9配位环境中。更值得注意的是，链1表现出单分子磁体（SMM）行为，其SMM性能在600 Oe的直流场感应条件下显着提高。由德拜模型拟合，的有效能垒1是17.8 K，和弛豫时间是2.4×10 -6 秒。链2的磁热效应测试进一步进行。当Δ H = 7 T 且T = 2 K 时，其-Δ S m达到最大值16.19 J K -1 kg -1。
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